Antiviral efficacy of cerium oxide nanoparticles

Abstract Nanomaterials have been proposed as good candidates for the elimination of viruses due to their multimodal mechanisms of action. Here, we tested the antiviral potential of cerium dioxide (CeO2) nanoparticles which is largely unexplored.Two types of nano-CeO2 particles with opposing surface charge, nano-CeO2(+) and nano-CeO2(-), were assessed for their capability to decrease the plaque forming units (PFU) of four enveloped and two non-enveloped viruses during 1 h exposure. Statistically significant antiviral activity of nano-CeO2 towards enveloped coronavirus SARS-CoV-2 and influenza virus A/WSN/1933 was registered already at 20 mg Ce/l. Significant decrease in PFU of other two enveloped viruses, transmissible gastroenteritis virus TGEV and bacteriophage φ6 was evidenced at 200 mg Ce/l. For all the enveloped viruses the maximum reduction of PFU after 1 h exposure to nano-CeO2 exceeded 2 logs, that has been considered as the lowest biologically meaningful activity in antiviral applications. For most of the enveloped viruses, 1 h exposure to nano-CeO2 resulted in ≥ 4 log reduction in PFU. As expected, the sensitivity of non-enveloped viruses towards nano-CeO2 was significantly lower than that of enveloped viruses. Until the highest tested concentration, 2000 mg Ce/l neither of the nano-CeO2 showed an effect on picornavirus EMCV and only nano-CeO2(-) caused a slight non-monotonic response in MS2 bacteriophage.Parallel testing of antiviral activity of Ce3+ ions and SiO2 nanoparticles allows to conclude that nano-CeO2 activity was due to neither released Ce3+ ions nor nonspecific effects of any nanosized particulate. Interestingly, we did not evidence any significant antiviral activity of Ag nanoparticles at 1 h exposure. This result referred to notably higher antiviral activity of nano-CeO2 compared with nanosilver that has been generally considered as active against viruses. Although exhibiting antiviral effects, the antibacterial activity of nano-CeO2 was very low. These results along with non-existent cytotoxicity nano-CeO2 allow us to propose nano-CeO2 for specific antiviral applications.